When a general motor operates, the rotor and the stator in the motor are mutually induced and become excited to thereby produce heat. The produced heat is not easily dissipated from the motor into ambient air and therefore tends to cause shortened service life of the motor. To improve the above problem, a water-cooling type motor is developed.
FIG. 16 is an exploded perspective view of a conventional water-cooling type motor, which includes a motor main body 30 and a heat-dissipation base 31. The motor main body 30 includes an enclosure 303, two covers 306 and 307, a rotor 301, and a stator 302 fitted around the rotor 301. The enclosure 303 internally defines a receiving space 3033 for receiving the heat-dissipation base 31 therein. The two covers 306, 307 are connected to two ends of the receiving space 3033. The enclosure 303 is further provided on an outer side 3031 thereof with an outlet 30311 and an inlet 30312 opposite to the outlet 30311.
The heat-dissipation base 31 has a hollow chamber 312 communicating with the receiving space 3033 for receiving the stator 302 and the rotor 301 therein. A flow passage 313 is provided around an outer circumferential surface of the heat-dissipation base 31 to communicate with the outlet 30311 and the inlet 30312. When the motor operates and produces heat, the heat-dissipation base 31 absorbs the heat from the stator 302 and the rotor 301. A type of cooling liquid, such as water or a coolant, circulates in the flow passage 313 to exchange heat with the heat-dissipation base 31, so as to achieve the purpose of heat dissipation.
While the heat produced by the conventional water-cooling type motor can be dissipated via the cooling liquid in the flow passage 313, the cooling liquid flows through the flow passage 313 at a relatively quick speed and therefore only stays in the heat-dissipation base 31 for a very short time, resulting in a poor heat exchange efficiency between the cooling liquid and the heat-dissipation base 31 and accordingly largely reduced heat dissipation effect.
More specifically, since the flow passage 313 in the conventional water-cooling type motor is a one-way smooth flow passage, the cooling liquid flows through the smooth flow passage 313 quickly and stays in the flow passage 313 only for a short time to carry away only a relative small quantity of heat from the heat-dissipation base 31. That is why the conventional water-cooling structure for the motor has low heat exchange efficiency and heat transfer effect, and accordingly low heat dissipation effect.
In brief, the conventional water-cooling structure for motor has the following disadvantages: (1) poor heat exchange efficiency; and (2) poor heat dissipation effect.
It is therefore tried by the inventor to develop an improved water-cooling structure for electric motor to overcome the drawbacks in the prior art.